FIG. 12 is a diagram showing the general configuration of a turret type punch press. The turret type punch press has an upper turret 1 that circumferentially supports a plurality of punch tools and a lower turret 2 that circumferentially supports a plurality of die tools 5. The upper turret 1 and the lower turret 2 are rotated to locate a desired set of the punch tool 4 and die tool 5 at a predetermined punch position P to punch a workpiece W that is a plate material.
Punching includes piercing and forming. Piercing involves fixing the die tool 5 so that its top surface is flush with a top surface of a workpiece table 18, and under this condition, lowering the punch tool 4 for piercing. Carrying out forming in a similar manner forms a formed part of the workpiece W below the top surface of the workpiece table 18. In this case, the formed part may interfere with the workpiece table 18 to hinder workpiece feeding. Thus, for forming, for example, upward forming, an upward protruding die tool for forming (hereinafter referred to as a “forming die”) 5 is used to form the workpiece W so that its formed part is formed above the top surface of the workpiece table 18.
Examples of such forming include a method of fixing the forming die 5 at a given position where the top surface of the forming die 5 is above the top surface 18a of the workpiece table 18 and lowering the punch tool 4 as shown in FIG. 13 and a method of fixing the punch tool 4 at a given position where a bottom surface of the punch tool 4 is at the same height as that of the top surface 18a of the workpiece table 18 and elevating the forming die 5 as shown in FIG. 14. FIG. 13A and FIG. 14A show conditions before forming, and FIG. 13B and FIG. 14B show conditions during forming. Where the punch tool 4 is lowered for forming as shown in the example in FIG. 13, the forming dies 5 located away from the punch position P are retracted to a lowering position below the top surface 18a of the workpiece table 18 in order to prevent hindrance to feeding of the workpiece W and damage to the back surface of the workpiece W. Thus, with either method for forming, the forming die 5 located at the punch position P needs to be elevated and lowered. The punch press is accordingly provided with an appropriate elevating and lowering device (for example, Japanese Patent No. 2889951).
The elevating and lowering device is composed of an advancing and retreating member formed as an inclined surface portion having a top surface inclined in one direction, and an actuator that advances and retreats the advancing and retreating member in the direction in which the inclined surface portion is inclined. With the inclined surface portion abutting against a part of the forming die located at the punch position, the advancing and retreating member is advanced or retreated to elevate or lower the forming die. According to Japanese Patent No. 2889951, the inclined surface portion of the advancing and retreating member is inclined in a direction orthogonal to a virtual straight line joining the punch position to the rotating center of the turret, that is, in a tangential direction of a circular trajectory along which the die tool is moved, and the advancing and retreating member also advances and retreats in this direction.
In the punch press according to Japanese Patent No. 2889951, the elevating and lowering device for the forming dies is fixed at the punch position. Further, the advancing and retreating member advances and retreats in the tangential direction to elevate and lower the forming dies. Accordingly, even while the forming dies are lowering, the advancing and retreating member is located immediately below the circular trajectory or its vicinity. Thus, where a plurality of forming dies are provided in the lower turret in proximity to one another, when one of the forming dies is located at the punch position, the advancing and retreating member may interfere with forming dies located close to the punch position. Increasing the advancing and retreating strokes of the advancing and retreating member can avoid this interference. However, this disadvantageously increases the size of the elevating and lowering device, and the time required for the forming dies to elevate and lower. As a result, where a plurality of forming dies are provided in the lower turret, they are forced to be spaced at intervals. This limits the number and positions of forming dies attached. Further, since the advancing and lowering member is always located below the turret, slag falling from the turret adheres to the advancing and retreating member, and its advancement and retreat guiding section. This may hinder the operation of the elevating and lowering device.
When the advancing and retreating member advances and retreats in the tangential direction as is the case with the conventional punch press, one elevating and lowering device can elevate and lower only the forming dies on one circumference. Thus, where the forming dies are provided on a plurality of concentric circles, as many elevating and lowering devices as the concentric circles must be provided. This complicates the structure of peripheral portion of the punch position.
An object of the present invention is to provide a punch press with forming dies which reduces the limitation on the number and positions of forming dies attached to the die supporting member and which enables a device that elevates and lowers the forming dies to operate appropriately without being affected by slag. Another object of the present invention is to reduce the moving distance of the device that elevates and lowers the forming dies and to facilitate the movement. Further another object of the present invention is to, where the forming dies are provided on each of plural concentric circles, enable a single device to elevate and lower the forming dies on each concentric circle. Further another object of the present invention is to facilitate the position switching of an elevating and lowering member, while supporting a die supporting member so that the die supporting member is movable in a horizontal direction.